The Elixir card increases the player's HP or MP rapidly for a few turns. At power level 2, both will be fully restored over 10 turns.
The Elixir card could be found in the following decks over the past several versions.
|0.11||0.12||0.13||0.14||0.15||0.16||0.17||0.18||0.19 and beyond|
The Elixir was one of the 23 cards to be kept in the deck simplification of 0.19, but most of the decks were removed.
Prior to 0.14, the HP or MP would be restored instantly.